We're talking about two different types of guests. For a guest specifically visiting for Avatar, this change would be either bad (if the alternative is no blockouts) or neutral (if the alternative is a resort-wide blockout). However, for the guests who are visiting for a general Walt Disney World vacation, it's better to be able to be able to attend MK, Epcot, and DHS with DAK blocked out than for Disney to block the entire resort and then that guest can't experience anything.
Maybe I'm incorrect in my assumption that the latter type of guest (primary goal of visiting WDW with secondary goal of visiting specific parks) outnumbers the former type of guest (primary goal of visiting a specific park).